From 254194dfc6b52463ff61ecf8f76fbfd1e702bc32 Mon Sep 17 00:00:00 2001
From: Johannes Schriewer <hallo@dunkelstern.de>
Date: Mon, 30 Jul 2018 22:13:37 +0200
Subject: [PATCH] Add client id sanity check

Re #10
---
 src/mqtt.c              |  6 ++++++
 tests/connect_publish.c | 12 ++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/mqtt.c b/src/mqtt.c
index b3ec0ce..4b8dc4b 100644
--- a/src/mqtt.c
+++ b/src/mqtt.c
@@ -183,6 +183,12 @@ static void _mqtt_connect(MQTTHandle *handle, MQTTEventHandler callback, void *c
 }
 
 MQTTHandle *mqtt_connect(MQTTConfig *config, MQTTEventHandler callback, void *context, MQTTErrorHandler error_callback) {
+    // sanity check
+    if ((config->client_id != NULL) && (strlen(config->client_id) > 23)) {
+        DEBUG_LOG("Client ID has to be shorter than 24 characters");
+        return NULL;
+    }
+
     MQTTHandle *handle = calloc(sizeof(struct _MQTTHandle), 1);
     initialize_platform(handle);
 
diff --git a/tests/connect_publish.c b/tests/connect_publish.c
index 23c18ec..5b95ec8 100644
--- a/tests/connect_publish.c
+++ b/tests/connect_publish.c
@@ -40,14 +40,22 @@ void mqtt_connected(MQTTHandle *handle, void *context) {
 int main(int argc, char **argv) {
     MQTTConfig config = { 0 };
 
-    config.client_id = "libmqtt_testsuite";
+    config.client_id = "libmqtt_testsuite_this_is_too_long";
     config.hostname = "localhost";
 
     config.last_will_topic = "testsuite/last_will";
     config.last_will_message = "RIP";
 
-    LOG("Trying to connect to %s", config.hostname);
+    LOG("Testing too long client id...");
     MQTTHandle *mqtt = mqtt_connect(&config, mqtt_connected, NULL, err_handler);
+    if (mqtt != NULL) {
+        LOG("Handle should be NULL, but it wasn't");
+        return 1;
+    }    
+
+    config.client_id = "libmqtt_testsuite";
+    LOG("Trying to connect to %s", config.hostname);
+    mqtt = mqtt_connect(&config, mqtt_connected, NULL, err_handler);
 
     if (mqtt == NULL) {
         LOG("Connection failed!");